[Zope] Pluggable Brains - Huh?

Well, I know they have a cool name. But thats about it. I have a problem that involves returning some data from a zCatalog, and some data from a Postgres database. Both items are treated as equivalent and should be displayed alphabetically side by side. I've got a marvelously kludgerific solution that involves copying the search results from the zCatalog into a list, which I can then insert my SQL based results in and sort as I see fit. I don't know if there is a better way, but I'd like to know more about Pluggable Brains so I can determine if there is. A search of Zope.org, and the list archives, comes up empty. Anyone with tips or resources? Edward